Oil recovery by in situ combustion



Jam 12, 1965 M. sANToURlAN 3,165,154

OIL RECOVERY BY IN SITU COMBUSTION Filed March 23. 1962 INVENTOR. M ELCON SANTOURI A N B77 QW 3,165,154 OIL RECVERY BY EN STFU QMEUSTIN Melcon Santourian, Bartlesville, Ghia., assigner to Phillips Petroleum Company, a corporation of Delaware Fiied Mar. 23, 1962, Ser. No. 182,'1i3

, iii Claims. (Ci. 16d-11) This invention relates to a process for recovering oil Yby in situ combustion from a permeable stratum containing hydrocarbons.

The recovery of oil by in situ combustion involves establishing a combustion zone within a carbonaceous stratum around an ignition well and moving the combustion zone thru the stratum to one or more offset wells either by direct injection of combustion-supporting gas, such as air, thru the ingnition well or thru the offset Well (or wells) so as to move the combustion zone inversely to the flow of said gas. The former technique is considered a direct drive process while the latter is usually designated an inverse drive process. It is, of course, desirable to ignite the stratum. throughout its entire thickness around the ignition well in order to produce as much stratum as possible on a given burnthru. However, it is difficult to ignite an oil-bearing stratum over the entire -to provide an improved process or technique for producing thick oil-bearing strata. Another object is to com- .bine a vertical drive inLsitu combustion process with a Yhorizontal drive processso as toproduce the entirethickness of the stratum being produced. A further object is -to provide an improved technique for igniting a permeable carbonaceous stratum around an ignition well thru- `out the thickness of the stratum. Other objectsoflhe invention Willbecorne Aapparent to one skilled in the art uplon consideration of the. accompanying disclosure. Y

A broad aspect of the invention comprises establishing ari-annular combustion zone around an ignition Well withi United StatesY Patent() v--ing' at higher and lower levels therein.

liild yPatented Jan. 12, 1955 ice panded by inverse drive with production thru the annulus of the well.

After combustion has been established in an annulus around the ignition well in the aforesaid manner, air is injected into the combustion Zone or thru the ignition well so as to advance the combustion zone toward the offset well or wells by direct' drive, or air is injected thru the offset well or wells so as to advance the annular combustion zone toward the injection Well or wells by inverse drive.

A more complete understanding of the invention may be had by reference to the accompanying drawing in which FlGURE l is an elevation in partial section thru an ignition'well and an offset well in a carbonaceous stratum illustrating one embodiment of the invention and FIG- URE 2 is a fragmentary elevation in partial section of another arrangement of apparatus in an ignition Well for effecting the invention.l

Referring to FIGURE 1, a carbonaceous stratum or oil sand it) is penetrated by an yignition well l2 and an offset well M. Well l2 is provided with casing 16 and tubing 1S extending from a lower level of the stratum thru the well head. A packer 20 is set ony tubing 18 at an intermediate level in stratum iii.

Well. 14 is provided with a casing 22 and a tubing Vat a lower level therein. In this arrangement there is an upper sectionfi) of stratum above packer 26 exposed' to the well and a lower section 32 Vbelowpacker k28 exposed to the well.

y It is Valso feasible to entend casirigs 16 and 22`rtliru stratum it?, providing perforations` are made in-the cas- However, due to the probabllrty of overheating and fusing yof the casing,

Ait is .preferred toA terminate thecasingtadjacent lthe top in an oil-hearing stratum which vextends from the top lto the-bottom of the stratum, by igniting the stratum adja- Vcent one end section ofthe annular zone and passing corn-l bustion-supporting gas vertically therethru so as to eX- .pand the combustion zone to the opposite end section of the anulus and, thereafter, passing combustion-supporting gas radially into the annular combution zone so as to -advance the same radially outwardly toward one or more Y offset wells in the Stratum. The anular combustion zone around the ignition well may be established by either Vdirect or inverse drive by inserting tubing inthe Well, po-

sitioning one or more packers on the tubing within the stratum, and feeding air or other combustion-supporting gas either thru the annulus and producing thru the tubing, v -or vice versa. The ignition may be leffected either inan ,upper section of the stratum above thepacker or packers or in a section of the stratumbelow the packer `or '..pacl-:ers. By igniting an upper section of the stratum and feeding air thru the well anulus, the Acombustion zone is Vexpanded by direct drive to the lower section of the stratum. .By igniting the upper section of the stratum I and injecting thru the tubing, the combustion Zone is ex- Y of the formation.

In operating with the arrangement illustrated in FIG- -URIE 1,.tl1`e.section of stratum 14E-.above packer Zi'is yignited lby means of a'charcoal pack l'which is ignitedby `dropping arailroad fusee` or other ignition' deviceon the charcoal and either Vpassing Vair or vother combustionlsupporting gas thruk tubi'ngjllS to establish an inverse ver'tical drive of the combustion 'zone yalongthe well. wall or thru line 19 and the -well an'nulus so as to drive the corn- 4.bustionzone by directy drive to, the lower section of the .stratum below packer 20. When Vair is injected thruthe annulus, Aproduced gasesare vented. thru tubing 18 and passed to separation and recovery apparatus (not shown). i .When air-'isinjected thru the tubing 18produced gases are passed thru line 19 to'recovery means..-

It `is alsojfeasib'le Vto place a charcoalor othersolid fuel. packin the bottom of well 12 Vbeforeyplacker 29 is positioned andhen-ignitinfg -the bottom of the fuel pack by dropping a fus'ee or other ignitordown the tubing string and either injecting vair thru the tubing string or thru' `line` 19 soy as to bur-n the fuel pack, ignite the adjacent stratum below. paclrerii, and drive the resulting combustion zone, around pacl erV29y into the upper section of the stratum.

A preferred arrangement of packers is illustrated in FIGURE 2. By igniting the stratum either above packer 26 or below packer 28 in the manner described above, and passing air either thru the annulus or thru ,the tubing, the ignited area is expanded from section 3G to section 32 or vice versa, depending upon where the ignition is initiated. This arrangement is more effective in extending the combustion zone in the stratum from the uppermost to the lowerrnost area thereof around well 12. The arrangement of FIGURE 2 is preferred when producing thick strata.

After establishing an annular combustion zone around well 12 extending substantially the thickness of the stratum, it is desirable to remove packer 2d or packers 26 and 2S, in case the arrangement of FIGURE 2 is utilized. Thereafter, in the event inverse drive of the combustion zone is to be practiced, air is injected thru well 14 so that it passes thru stratum lil into the combustion zone around well 12, thereby causing the combustion zone to advance toward well i4. Of course, the annular cornbustion zone around well 12 is preferably advanced radially outwardly into the stratum in all directions by injecting air thru` a ring of surrounding wells. In the event direct drive of the annular combustion zone is to be utilized, air is injected thru well 12 and the combustion front is driven toward the surrounding wells 1d with production being recovered thru tubing 24. or the annulus and line 25.

In thick strata containing highly viscous oil, it is impossible to utilize direct drive either vertically along the ignition well or horizontally toward the offset wells. With such strata, direct drive of the combustion zone causes plugging of the stratum due to the driving of hot liquid oil Iinto the cool stratum outside the combustion zone where the oil congeals and prevents flow of gases thru the stratum, thereby preventing arrival of air in the cornbustionv zone and causing the lire to die out. Hence, in most strata it is preferred and necessary to utilize inverse drive of the combustion fronts or zones.

It is impossible to advance a combustion front by inverse drive using inverse air injection thru the offset t Wells in strata'containing substantially no gaseous hydrocarbon.r In operating in such strata it is necessary to .incorporate in the injected air or other combustion-supporting gas from 1 to 3 or 4 volume percent of fuel gas, such as the Vlight normally gaseous hydrocarbons or L.P.G. The arrival of the fuel in the combustion front in admix- Vture with excess oxygen causes the combustion of the fuel gas which maintains a suiliciently high ltemperature Vin the combustion front to burn some of the inpiace khydrocarbons and produce oil from the stratum.

Itiris'within the scope of the invention to ignite the stratumA by any suitablemeans, although ignition with a,

Vcharcoal pack burned in contact with the stratum by passing air thereto (which may contain a small concentration of fuel gas) is preferred. The essence of the invenftion is the establishment of an annular combustion zone Well and atleast one oifsetwell which comprises providing said ignition well with a tubing string extending to a lower level Vof said stratum; positioning a packer around vsaid tubing at an intermediate level of said stratum dividing same 4into an upper level and a lower level; while maintaining said at least one offset well closed in, conducting a first combustion `phase by igniting said lstratum at Aa selected one'of rsaid upper and'said lower level; passing t d combustion-supporting gas directly into the resulting cornbustion zone at the selected level from one of the tubing and the annulus of said ignition well so as to expand said zone thru an annular section of stratum to the other of said levels by direct drive; thereafter conducting a second combustion phase by passing said gas to the resulting annular combustion zone from one of said ignition well and said offset well so as to move said combustion zone toward said offset well; and recovering hydrocarbons produced by the second phase combustion from one of said wells.

2. The process of claim l wherein said stratum is ignited at said upper level; said combustion-supporting gas is injected thru the ignition well annulus so as to move said combustion zone by direct drive to said lower level; and gases produced by said first combustion phase are produced thru said tubing string.

3. The process of claim l wherein said combustionsupporting gas for said second combustion phase is injected thru said at least one offset well so as to move said zone by inverse drive toward said offset well; and gases produced by said second combustion phase are recovered from said ignition well.

4. The process of claim l wherein said combustion-supporting gas for said second combustion phase is injected thru said ignition well so as to move said combustion zone by direct drive toward said at least one offset well; and gases produced during said second combustion phase are recovered from said at least one offset well.

5. A process for producing hydrocarbons from a permeable carbonaceous stratum penetrated by an ignition well and at least one offset well which comprises providing said ignition Well with a tubing string extending to a lower level of said stratum; positioning upper and lower packers on said tubing string at upper and lower levels of said stratum so as to leave an upper section of said stratum above said upper packer directly accessible thru the well annulus and a lower section of said stratum below said lower packer directly accessible thru said tubing; conducting a first combustion phase around said ignition well, while maintaining said at least one offset well closed in, by igniting one of said upper and lower sections; passing combustion-supporting gas directly into the resulting combustion zone from one of the tubing and annulus of said ignition well so as to expand said zone by direct drive thru an annular section of said stratum surrounding said ignition well and including said upper and lower sections; thereafter removing said packers and conducting a second combustion phase by passing combustion-supporting gas thru one of said ignition well and said otfset well to the annular combustion zone so as to advance said zone thru said stratum toward said offset well; and recovering produced gases from said second combustion phase from one of said ignition well and said offset well.

6. The process of claim 5 wherein said upper section is ignited, said combustion-supporting gas is passed to the combustion zone thru said annulus, and gases produced by said first combustion phase are recovered thru the tubing.

7. The process of claim 5 wherein said lower section is ignited, said combustion supporting gas is passed to the combustion zone thru the tubing, and gases produced during said first combustion phase are recovered thru said annulus.

8. The process of claim 5 wherein said combustionsupporting gas for said second combustion phase is injected thru said at least one offset well so as to advance said combustion zone inversely to the iiow of said gas, and produced gases from said second combustion phase are recovered thru said ignition well.

9. The process of claim 5 wherein said combustion-supporting gas for said second combustion phase is injected thrujsaid ignition well so as to advance said combustion zone by direct drive, and produced gases from said second 5 combustion phase are recovered from said at least one olset Well.

10. A process for producing hydrocarbons from a permeable carbonaceous stratum penetrated by an ignition Well and at least one offset well which comprises establishing an annular combustion zone around said ignition well extending substantially from the top to the bottom of said stratum by igniting said stratum adjacent one end section of said annulus and passing combustion-supporting gas directly into the ignited section of said annulus so as to expand the resulting combustion zone to the opposite end section of said annulus; thereafter passing combustionsupporting gas thru said at least one olfset well and thru said `stratum to said annular combustion zone so as toV References Cited in the le of this patent UNITED n STATES PATENTS Sirnm Mar. 27, 1962 Dixon July 17, 1962 

10. A PROCESS FOR PRODUCING HYDROCARBONS FOR A PERMEABLE CARBONACEOUS STRATUM PENETRATED BY AN IGNITION WELL AND AT LEAST ONE OFFSET WELL WHICH COMPRISES ESTABLISHING AN ANNULAR COMBUSTION ZONE AROUND SAID IGNITION WELL EXTENDING SUBSTANTIALLY FROM THE TOP TO THE BOTTOM OF SAID STRATUM BY IGINTING SAID STRATUM ADJACENT ONE END SECTION OF SAID ANNULUS AND PASSING COMBUSTION-SUPPORTING GAS DIRECTLY INTO THE IGNITED SECTION OF SAID ANNULUS SO AS TO EXPAND THE RESULTING COMBUSTION ZONE TO THE OPPOSITE END SECTION OF SAID ANNULUS; THEREAFTER PASSING COMBUSTIONSUPPORTING GAS THRU SAID AT LEAST ON OFFSET WELL AND THRU SAID STRATUM TO SAID ANNULAR COMBUSTION ZONE SO AS TO ADVANCE SAID ZONE TOWARD SAID OFFSET WELL; AND RECOVERING PRODUCED GASES FROM SAID IGNITION WELL. 